1. Field of the Invention
The present invention relates to a magneto-optical recording medium in and from which information can be recorded, reproduced and erased by utilizing light beams, and a process for producing it.
2. Related Background Art
In recent years, as large-capacity information recording means, optical memories such as optical disks are energetically developed and marketed. In particular, information-erasable/rewritable magneto-optical recording mediums have attracted notice.
Conventional magneto-optical recording mediums, however, require two steps when recorded information is rewritten, which are the steps of erasing recorded old information and thereafter recording new information, and have had a problem in making the data transfer speed higher. To cope with such a problem, proposals are made on a magnetic-field modulation system that requires no erasure of old information when information is rewritten, i.e., a system in which, while a magneto-optical recording medium is irradiated with laser beams having a constant intensity, a magnetic field applied is modulated according to information signals to make a record.
Incidentally, when the above magnetic-field modulation system is employed in the recording of information in magneto-optical disks, a magnetic head must be made to have a low inductance in order to increase switching speed in the direction of external magnetic field to improve the transfer speed. This, however, is accompanied with a lowering of magnetic field sensitivity, and hence it is preferable for the magnetic head to be made as close as possible to a magneto-optical recording layer (see FIG. 8).
In such a case, however, since the magnetic head is rubbed against a protective layer provided on the magneto-optical recording layer when stopped, there has been the problem that the magnetic head and the protective layer cause electrostatic attraction between them to make it difficult to drive the magnetic head and the magneto-optical disk.
Thus, as a countermeasure to such a problem, the present applicants have proposed in Japanese Patent Application Laid-open No. 4-64939 to disperse a conductive inorganic filler such as tin oxide in the protective layer so that the surface electric resistance of the protective layer is decreased to prevent electrostatic attraction between the magnetic head and the protective layer.
Such constitution is effective for preventing the electrostatic attraction between the magnetic head and the protective layer, but tends to result in a lowering of recording sensitivity of the magneto-optical disk, also making the shape of recording pits non-uniform to bring about the problem of a decrease in C/N ratio of reproducing signals of recorded information.